use-python-x402-core-avm

Import register_exact_avm_client from x402.mechanisms.avm.exact, create an x402Client instance, and call register_exact_avm_client(client, signer) with a ClientAvmSigner implementation. The client then handles 402 responses automatically on fetch calls.

Implement the ClientAvmSigner protocol with an address property and a sign_transactions method that accepts raw msgpack bytes. Convert raw bytes to base64 before calling algosdk encoding.msgpack_decode, sign with a base64 private key, and convert back to raw bytes.

Fee abstraction uses a two-transaction atomic group: a USDC transfer with zero fee signed by the client, and a self-payment from the fee payer covering both fees signed by the facilitator. Both transactions execute atomically, so the client never needs ALGO for fees.

The Python algosdk msgpack_decode expects a base64 string, not raw bytes. Wrap raw bytes with base64.b64encode(raw).decode() before decoding, and base64-decode the output of msgpack_encode when converting back to raw bytes.

Yes, the SDK provides ALGORAND_MAINNET_CAIP2 and ALGORAND_TESTNET_CAIP2 constants with corresponding USDC ASA IDs (31566704 mainnet, 10458941 testnet). Facilitators can register multiple networks in a single register_exact_avm_facilitator call.

Python 3.10 or later is required. Install the package with pip install "x402-avm[avm]" for the core AVM mechanism, or add framework extras like "x402-avm[avm,fastapi]" for web framework integration.